QUESTION

While travelling to the cottage this year, I noticed that the Ministry of Transportation was tearing up large sections of the 400-series highways and posting warnings about the “grooved pavement.” Why can’t they just take off the top layer and put down a new layer in the same go?

ANSWER

Ideally, that’s what they like to do. It is possible for machines to remove the top layer of pavement and put down a new one immediately, usually overnight. A machine cuts out pieces of the old, damaged road—a process called milling—then a new surface of hot-mix asphalt, a combination of crushed stones and gravel held together with liquid asphalt cement, is laid down. Sometimes, because machines are not available or as a result of weather delays, that bumpy, teeth-rattling milled surface is exposed for longer, usually a maximum of 72 hours.

Why do so many road repairs seem to drag…on…forever? According to Sandy Brown, technical director of the Ontario Hot Mix Producers Association and the Canadian regional engineer for the Asphalt Institute, there are two situations when “shave and pave” projects slow down. One is when the work is done in stages so that enough lanes stay open to maintain the flow of traffic. The other happens during the winter, when unplanned milling procedures are needed as a result of rapid freezing and thawing. At that time, repaving can be delayed by up to eight months, Brown explains, until it’s warm enough to put down hot-mix asphalt, which must be mixed, placed, and compacted at high temperatures. In addition, while a typical repaving job covers a stretch of highway six to 12 km long, the contractor might tackle it one kilometre at a time. Math lesson: If it takes three days to complete a one-kilometre section, that’s potentially 36 days of roadwork.

“The grooved pavement is not comfortable to drive on,” Brown admits. But heck, it’s a lot better than driving your car into a giant pothole at 100 km/h.

* Published in the Summer 2009 issue of Cottage Life